Created module idea-test-framework and moved classes needed for idea tests there

Moved tests for completion and their test data into module idea-completion

idea/idea-completion/testData/handlers/smart/NestedDataClassComma.kt.after

@@ -0,0 +1,9 @@
+class Outer {
+    private data class Nested(val v: Int, val v2: Int)
+
+    fun foo(p: Int): Inner {
+        return Outer.Nested(p, <caret>)
+    }
+}
+
+// ELEMENT: p